Electric wire conductor, covered electric wire, and wiring harness

ABSTRACT

A wiring harness comprises a first covered electric wire, and a second covered electric wire. The first covered electric wire comprises a first electric wire conductor made of aluminum or an aluminum alloy and an insulator covering the first electric wire conductor. The first electric wire conductor comprises a wire strand of a plurality of elemental wires twisted together, and has a flat portion where a cross-section of the wire strand intersecting an axial direction of the wire strand has a flat shape. The second covered electric wire comprises a second electric wire conductor made of copper or a copper alloy and an insulator covering the second electric wire conductor. The second electric wire conductor has a lower flatness and a smaller conductor cross-sectional area than the first electric wire conductor of the first covered electric wire.

This application is a continuation of U.S. patent application Ser. No.16/842,828 filed on Apr. 8, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/342,505 filed on Apr. 16, 2019 (now issued asU.S. Pat. No. 10,658,092), which is a National Stage Entry ofPCT/JP2017/040208 filed on Nov. 8, 2017, which claims priority toPCT/JP2017/012924 filed on Mar. 29, 2017, Japanese Patent ApplicationNo. 2017-022905 filed on Feb. 10, 2017, and Japanese Patent ApplicationNo. 2016-218236 filed on Nov. 8, 2016. Entire contents of each of theabove-identified documents are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an electric wire conductor, a coveredelectric wire, and a wiring harness, and more specifically, to anelectric wire conductor made of a wire strand, a covered electric wirecontaining an insulator on an outer periphery of the electric wireconductor, and a wiring harness including the covered electric wire.

BACKGROUND ART

A flat cable containing a flat-shaped conductor is commonly known. Aflat cable occupies a smaller space for routing than a conventionalelectric wire configured with a conductor having a substantiallycircular cross-section.

As described in Patent Literature 1, a flat rectangular conductor isoften used as a conductor for conventional flat cable. The rectangularflat conductor is made of a single metal wire formed to have arectangular cross-section.

CITATION LIST Patent Literature

Patent Literature 1: JP 2014-130739 A

SUMMARY OF INVENTION Problems to be Solved by the Invention

A flat rectangular conductor has comparatively high flexibility, andeasily bends in a height (thickness) direction of the flatcross-section. However, in a width direction of the flat cross-section,the conductor has low flexibility, and is too rigid to bend easily.Thus, the flat cable having the rectangular conductor hardly bends inthe particular direction, which lowers workability of the cable uponrouted.

The present invention has been made to solve the above problems, and anobject of the present invention is to provide an electric wire conductorhaving both flexibility and a space-saving property, a covered electricwire, and a wiring harness including such an electric wire conductor.

Means of solving the problems

To achieve the objects and in accordance with the purpose of the presentinvention, an electric wire conductor according to the present inventioncontains a wire strand containing a plurality of elemental wires twistedtogether, the conductor having a flat portion where a cross-section ofthe wire strand intersecting an axial direction of the wire strand has aflat shape, the flat portion having a vacancy ratio of 17% or higher,the vacancy ratio defined as a ratio of vacancies not occupied by theelemental wires in the cross-section of the flat portion.

Here, the vacancy ratio is preferably 40% or lower.

The deformation ratios of the elemental wires from a circle in thecross-section of the flat portion are preferably lower at a part facingan outer periphery of the flat portion than at a center part of the flatportion. Further, the deformation ratios of the elemental wires from acircle at the part facing the outer periphery of the flat portion are50% or lower of the deformation ratios of the elemental wires at thecenter part of the flat portion. Furthermore, the deformation ratios ofthe elemental wires from a circle in the cross-section of the elementalwires in the cross-section of the flat portion at the part facing theouter periphery of the flat portion are preferably 10% or lower.

The electric wire conductor preferably contains a continuous vacancy inthe cross-section of the flat portion which is capable of accommodatingtwo or more of the elemental wires.

The cross-section of the flat portion preferably includes opposing edgesalong the width direction of the flat shape being parallel to eachother. In this case, the deformation ratios of the elemental wires froma circle in the cross-section of the flat portion are preferably lowerat end parts of the opposing sides of the flat portion than at thecenter part of the flat portion.

A length in the width direction of the flat shape of the flat portion ispreferably three times or more larger than a length in the heightdirection intersecting the width direction.

The cross-section of the flat portion preferably has a quadrangularshape. Further, the cross-section of the flat portion preferably has arectangular shape.

The electric wire conductor preferably contains the flat portion and alow-flatness portion having a flatness lower than the flat portion, theflat portion and the low-flatness portion continuously disposed in theaxial direction.

The number of elemental wires contained in the wire strand is preferably50 or more.

The wire strand is preferably made of copper or a copper alloy and has aconductor cross-sectional area of 100 mm² or larger, or made of aluminumor an aluminum alloy and has a conductor cross-sectional area of 130 mm²or larger.

In the flat portion of the electric wire conductor, the wire strand ispreferably pressed from a first direction and a second directionopposing to each other, and from a third direction and a fourthdirection opposing to each other and intersecting the first directionand the second direction.

A covered electric wire according to the present invention contains theelectric wire conductor as described above and an insulator covering theelectric wire conductor.

A wiring harness according to the present invention contains the coveredelectric wire as described above.

Here, the wiring harness preferably contains a plurality of theabove-mentioned covered electric wires aligned along at least one of thewidth direction of the electric wire conductor and a height directionintersecting the width direction. In this case, the wiring harnesspreferably contains at least one of a heat dissipation sheet disposedbetween the plurality of the covered electric wires and a heatdissipation sheet commonly contacting the plurality of the coveredelectric wires. Further, the plurality of the covered electric wires arepreferably aligned at least along the height direction. In this case,interposing sheets made of a heat dissipation material are preferablydisposed between the plurality of the covered electric wires alignedalong the height direction. Further, a connection member made of a heatdissipation material is preferably disposed mutually connecting theinterposing sheets.

The wiring harness is preferably disposed along an outer periphery of acolumnar member. Alternatively, the wiring harness is preferably housedin a hollow part of a hollow tubular member having an opening along thelongitudinal direction.

Further, the wiring harness is preferably disposed under the floor of anautomobile to constitute a power-supply trunk line. Furthermore, thewiring harness preferably constitutes the ceiling or the floor of anautomobile. In these cases, the wiring harness preferably contains aplurality of the above-mentioned covered electric wires which arealigned at least along the width direction of the electric wireconductor, have uniform length in a height direction intersecting thewidth direction, and are disposed between an interior member and a soundabsorbing member of the automobile so as to dispose the width directionalong surfaces of the interior member and the sound absorbing member.

The wiring harness preferably contains a first covered electric wire anda second covered electric wire, in which the first covered electric wireis the above described covered electric wire having the electric wireconductor made of aluminum or an aluminum alloy, and the second coveredelectric wire has the electric wire conductor made of copper or a copperalloy having a lower flatness and a smaller conductor cross-sectionalarea than the electric wire conductor of the first covered electricwire. In this case, the conductor cross-sectional area of the secondcovered electric wire is preferably 0.13 mm² or smaller.

Advantageous Effects of Invention

The electric wire conductor according to the present invention has highflexibility because it is formed of a wire strand but not of a singlewire. Further, the flat portion having the flat cross-sectioncontributes to reduce a space required for routing as an electric wirecompared with a conventional electric wire conductor having asubstantially circular cross-section. Furthermore, in a case where theconductor cross-sectional area is made large, a length in the heightdirection can be kept small by increasing a length in the widthdirection of the flat shape, whereby the conductor cross-sectional areacan be increased while maintaining the space-saving property.

In addition, having a vacancy ratio of 17% or higher, the electric wireconductor according to the present invention can effectively maintainexcellent flexibility even through it has a flat cross-section. As aresult, the electric wire conductor can be routed freely.

Here, when the vacancy ratio is 40% or lower, the flat portion can beformed into a sufficiently flat shape. Also, the flat shape thus formedcan be effectively maintained. Accordingly, the space-saving property ofthe electric wire conductor can be effectively enhanced.

When the deformation ratios of the elemental wires from a circle in thecross-section of the flat portion are lower at the part facing the outerperiphery of the flat portion than at the center part of the flatportion, intensive deformations of the elemental wires located in theperipheral part and application of a large load to the wires due to thedeformation for forming the wire strand to have a flat cross-section canbe prevented. Further, formation of an irregular structure can beprevented including a sharp protrusion to be formed on the peripheralpart of the electric wire conductor due to the deformation of theelemental wires.

When the deformation ratios of the elemental wires from a circle at thepart facing the outer periphery of the flat portion are 50% or lower ofthe deformation ratios of the elemental wires at the center part of theflat portion, concentration of the deformation and the load on theperipheral part of the wire strand, and formation of the irregularstructure on the surface of the electric wire conductor is effectivelyprevented.

When the deformation ratios of the elemental wires from a circle at thepart facing the outer periphery of the flat portion are 10% or lower,concentration of the deformation and the load on the peripheral part ofthe wire strand, and formation of the irregular structure on the surfaceof the electric wire conductor are effectively prevented.

When the electric wire conductor includes a continuous vacancy in thecross-section of the flat portion which is capable of accommodating twoor more of the elemental wires, the electric wire conductor can bendflexibly through migration of the elemental wire to the vacancy, thusthe electric wire conductor effectively achieves high flexibility.

When the cross-section of the flat portion includes opposing edges beingparallel to each other along the width direction of the flat shape, alarge space can be effectively provided on the outside in the height(i.e., thickness) direction of the electric wire to be routed, whichleads to high space-saving property of the electric wire. In particular,when a plurality of electric wires are stacked when routed, anunnecessary large space is not required.

In this case, when the deformations ratio of the elemental wire from acircle in the cross-section of the flat portion at the end parts of theopposing edges being parallel to each other of the flat portion arelower than the deformation ratios of the elemental wires at the centerpart of the flat portion, the concentration of deformation and load onthe end parts of the electric wire conductor can be prevented. Further,an irregular structure tends to be formed especially on the end parts ofthe opposing edges being parallel to each other within the peripheralpart of the electric wire conductor; however, by keeping the deformationratios of the elemental wire at the end parts small, the formation ofthe irregular structure including the sharp protrusion on the edge partscan be prevented effectively.

When the length in the width direction of the flat shape of the flatportion is three times or more larger than the length in the heightdirection intersecting the width direction, the electric wire conductorhas high flexibility while having high space-saving property in theheight direction resulting from the smaller length in the heightdirection with respect to the length in the width direction.

Further, when the cross-section of the flat portion is a quadrangularshape, useless spaces between electric wires are reduced when aplurality of the electric wires are aligned or stacked, whereby theelectric wires can be assembled densely.

Furthermore, when the cross-section of the flat portion is a rectangularshape, useless spaces between the electric wires are especially reducedwhen aligning or stacking a plurality of the electric wires, achievingthe remarkably excellent space-saving property.

When the electric wire conductor contains the flat portion and thelow-flatness portion having a flatness lower than the flat portion thatare disposed continuously in the axial direction, the portions with thedifferent flatness may be disposed in one electric wire conductor,whereby the conductor has the properties of the both portionssimultaneously without a process such as joining. For example, arrangingthe flat portion in a center part of the electric wire conductor, andarranging the low-flatness portions having a substantially circularcross-section on both ends of the flat portion can achieve both thespace-saving property at the center part and convenience in attachingmembers such as terminals to the end parts of the electric wireconductor.

When the number of elemental wires contained in the wire strand is 50 ormore, the wire strand can be effectively formed into a flatcross-section without drastically deforming each elemental wire byutilizing a change in the relative arrangement of the elemental wires,while leaving large vacancies between the elemental wires. Thus, theelectric wire conductor effectively achieves both the space-savingproperty and the flexibility.

When the wire strand is made of copper or a copper alloy and has aconductor cross-sectional area of 100 mm² or more, or made of aluminumor an aluminum alloy and has a conductor cross-sectional area of 130 mm²or more, the space-saving property and flexibility achieved by the flatcross-sectional shape are particularly effective. For the electric wireconductor having a large cross-sectional area of 100 mm² or more, or 130mm² or more, if the cross-section is substantially circular, a largespace is required for routing due to largeness of the diameter and anopposing force against bending becomes large. However, when thecross-section is made flat, the electric wire conductor having such alarge cross-sectional area can achieve the space-saving property as wellas the high flexibility especially for the bending in the heightdirection.

In addition, in the flat portion of the electric wire conductor, whenthe wire strand is pressed from the first direction and the seconddirection opposing to each other, and from the third direction and thefourth direction opposing to each other and intersecting the firstdirection and the second direction, the electric wire conductor can beeffectively formed to have a substantially quadrangle cross-section,thus achieving the excellent space-saving property.

Since the covered electric wire according to the present inventioncontains the electric wire conductor as described above, the coveredelectric wire has both flexibility resulting from the electric wireconductor being a wire strand and space-saving property resulting fromthe electric wire conductor having a flat shape. Therefore, in the casewhere the plurality of the covered electric wires are aligned or stackedwhen routed, the routing can be carried out with high degree of freedomwhile saving the space.

As the wiring harness according to the present invention contains thecovered electric wire containing the flat electric wire conductor asdescribed above, it has excellent flexibility and space-saving property,and thus can be suitably used as a wiring material in a limited spacesuch as an automobile.

Here, when the wiring harness contains a plurality of the coveredelectric wires as described above, and the plurality of the coveredelectric wire are aligned along at least one of the width direction ofthe electric wire conductor and the height direction intersecting thewidth direction, the wiring harness can be formed while reducing thespaces between the plurality of the covered electric wires, thus havingthe remarkably high space-saving property.

In this case, when the wiring harness contains at least one of the heatdissipation sheets interposed between the plurality of the coveredelectric wires and the heat dissipation sheet commonly contacting theplurality of the covered electric wires, even when the plurality of thecovered electric wires are densely arranged to be close to each otherutilizing the space-saving property resulting from the flat shape, theinfluence of heat generated upon application of an electric current canbe suppressed.

Further, when the plurality of the covered electric wires are arrangedat least along the height direction, the covered electric wires can beeffectively routed in a variety of small spaces such as a thin space byutilizing the arrangement of the covered electric wires in the heightdirection.

In this case, when the interposing sheets made of the heat dissipationmaterial are disposed between the plurality of the covered electricwires aligned along the height direction, and the connection member madeof the heat dissipation material is disposed to mutually connect theplurality of the interposing sheets, the following effect is obtained:the interposing sheets disposed between the covered electric wireseffectively promotes heat dissipation though outward dissipation of theheat generated upon application of a current tends to be difficult in acase where a plurality of the covered electric wires are arrangedclosely making their flat wide surfaces to oppose one another.

When the wiring harness is disposed along the outer periphery of acolumnar member, or the wiring harness is housed in the hollow part of ahollow tubular member having an opening along the longitudinaldirection, the columnar member or the tubular member can be used forsupporting the wiring harness, whereby the routing space of the wiringharness is effectively reduced.

Further, when the wiring harness is disposed under the floor of anautomobile to constitute the power-supply trunk line, compared with aconventional power-supply trunk line using a copper plate, theproductivity can be enhanced and the fatigue fracture due to the enginevibration, for example, can be suppressed.

When the wiring harness constitutes the ceiling or the floor of anautomobile, the space in the automobile can be further effectively usedto provide a wiring route, and the high heat dissipation performance canbe achieved also in the case of applying a large electric current.Further, a ceiling surface or a floor surface of any shape can be formedin accordance with the arrangement of the covered electric wires.

In these cases, the wiring harness may contain the plurality of coveredelectric wires as described above which are aligned at least along thewidth direction of the electric wire conductor, have uniform length inthe height direction intersecting the width direction, and are disposedbetween the interior member and the sound absorbing member of theautomobile so as to dispose the width direction along the surfaces ofthe interior member and the sound absorbing member. In this case, thespace between the interior member and the sound absorbing member can beeffectively used for routing the wiring harness while the distancebetween the interior member and the sound absorbing member is keptsmall. Further, since the height of the plurality of covered electricwires is uniform, the irregular structure of the covered electric wirehardly influences a surface shape of the interior member or a soundabsorbing property of the sound absorbing member.

Further, when the wiring harness contains the first covered electricwire and the second covered electric wire, in which the first coveredelectric wire is the above described covered electric wire having theelectric wire conductor made of aluminum or an aluminum alloy, and thesecond covered electric wire has the electric wire conductor made ofcopper or a copper alloy having a lower flatness and a smaller conductorcross-sectional area than the electric wire conductor of the firstcovered electric wire, the space occupied by the first covered electricwire, which tends to have a large area because of the low electricalconductivity of aluminum and the aluminum alloy, can be reduced, andsimultaneously, characteristics of the second covered electric wirebrought about by the copper or copper alloy such as the high electricalconductivity in the second covered electric wire can be used.

In this case, when the conductor cross-sectional area of the secondcovered electric wire is 0.13 mm² or smaller, the entire wiring harnesscan effectively have a high space-saving property.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an electric wire conductor according toone embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electric wire conductor.

FIG. 3 is a cross-sectional view which illustrates rolling of a raw wirestrand.

FIGS. 4A to 4D are views showing a variety of cross-sectional shapes ofthe electric wire conductor, and FIGS. 4A to 4D respectively showdifferent shapes. In FIGS. 4B to 4D, elemental wires are omitted.

FIGS. 5A and 5B are cross-sectional views that illustrate examples ofarrangement of covered electric wires in a wiring harness according toone embodiment of the present invention. FIG. 5A illustrates a casewhere the covered electric wires are aligned in a width direction, andFIG. 5B illustrates a case where the covered electric wires are alignedin a height direction.

FIG. 6 is a cross-sectional view showing another embodiment where thecovered electric wires are aligned in the width direction.

FIGS. 7A and 7B are views illustrating examples of routing structure ofthe wiring harness. FIG. 7A illustrates a routing structure with acylindrical member, and FIG. 7B illustrates a routing structure with atubular member having a channel-shaped cross-section.

FIGS. 8A to 8C are photographic images of cross-sections of the coveredelectric wires. FIG. 8A shows a raw wire strand before pressing, FIG. 8Bshows Sample 1 with a low compression ratio, and FIG. 8C is Sample 2with a high compression ratio.

FIG. 9 shows simulation results regarding a temperature rise of thecovered electric wires.

DESCRIPTION OF EMBODIMENTS

Hereinafter, detailed descriptions of an electric wire conductor, acovered electric wire, and a wiring harness according to one embodimentof the present invention will be provided with reference to FIGS. 1 to 9. A covered electric wire according to one embodiment of the presentinvention contains an electric wire conductor according to oneembodiment of the present invention and an insulator covering theconductor. In addition, a wiring harness according to one embodiment ofthe present invention contains a plurality of covered electric wiresassembled together containing the covered electric wire according to oneembodiment of the present invention.

[Electric Wire Conductor]

FIG. 1 is a perspective view of an external appearance of an electricwire conductor 10 according to one embodiment of the present invention.FIG. 2 shows a cross-section perpendicularly intersecting an axialdirection (longitudinal direction) of the electric wire conductor 10.

(1) Cross-Sectional Shape of the Electric Wire Conductor

The electric wire conductor 10 is configured as a wire strand containinga plurality of elemental wires 1 twisted together. Further, at least apart of the electric wire conductor 10 along the axial direction has aflat outer shape. In other words, the electric wire conductor 10 has aflat portion where a cross-section perpendicularly intersecting theaxial direction of the electric wire conductor 10 is flat. In thepresent embodiment, the entire electric wire conductor 10 along theaxial direction is formed as the flat portion.

Here, the concept that “the cross-section of the electric wire conductor10 is flat” describes a state where a width W, which is a length of thelongest line among lines that pass through the cross-section in parallelto edges constituting the cross-section and encompass the entirecross-section, is larger than a height H, which is a length of a lineperpendicular to the above-mentioned longest line and encompass theentire cross-section. In the cross-section of the electric wireconductor 10 according to the present embodiment shown in FIG. 2 , andin each of the cross-sections of the electric wire conductors in theembodiments shown in FIGS. 4A to 4D, the width W is larger than theheight H.

While the cross-section of the electric wire conductor 10 may have anyspecific shape as long as it is flat, the cross-section of the electricwire conductor 10 in the present embodiment has opposing edges 11 and 12that are parallel to each other along a direction of width W (widthdirection x) of the flat shape. In other words, two parallel lines 11and 12 can be drawn in the width direction x, so as to circumscribe theouter elemental wires 1 forming the cross-section of the electric wireconductor 10. In the present description, concerning the shape of theelectric wire conductor 10, concepts for describing relationships amonglines and surfaces such as parallel and vertical may include a deviationwith reference to the concepts in geometry such as a deviation at anangle of approximately plus or minus 15 degrees, or an R shape whereeach corner is rounded. In addition, concepts of edges, straight lines,plain surfaces, or the like may include a curved line or a curvedsurface with a deviation at an angle of approximately plus or minus 15degrees from a geometric straight line or a plain surface.

In the present embodiment, the cross-section of the electric wireconductor 10 has a rectangular shape. In the Figures, the number ofelemental wires 1 contained in the electric wire conductor 10 is reducedfor easier understanding.

As the electric wire conductor 10 according to the present embodimenthas a flat cross-section, when it is routed in a form of the coveredelectric wire, for example, a space necessary for routing may be madesmaller than a case of routing an electric wire having a substantiallycircular cross-section of the same conductor cross-sectional area as theelectric wire conductor. In other words, spaces around an electric wirein which other electric wires or other members are not allowed to bedisposed can be reduced. In particular, a space occupied by the electricwire in a height direction y can be made smaller. Thus, the electricwire effectively achieves a space-saving property. Consequently, otherelectric wires or other members can be sufficiently disposed in a spacevertically provided in the height direction (±y direction) outside ofthe electric wire. For example, in the case of routing the electric wirealong a surface for routing, when a flat surface of the electric wire,that is, a surface parallel to the width direction x is arranged alongthe surface for routing, it is possible to effectively provide a spaceabove the electric wire (in a direction opposing to the surface forrouting, having the electric wire therebetween) . Further, in a casewhere a conductor cross-sectional area of the electric wire conductor 10is desired to be large, the space-saving property in the heightdirection y can be maintained by making the width W large while keepingthe height H small.

In particular, the electric wire conductor 10 having opposing edges 11and 12 parallel to the width direction x in its cross-section canprovide a large space vertically in the height direction (±y direction)outside the routed electric wire, whereby an excellent space-savingproperty is achieved. Especially, in the case of assembling a pluralityof electric wires by stacking one electric wire on another electricwire, spaces between the plurality of electric wires along the heightdirection y can be reduced. Here, the concept of “assembling a pluralityof electric wires” includes both of a configuration where a plurality ofelectric wires are integrally bundled with an insulation material, forexample, and a configuration where a plurality of independent electricwires are closely disposed.

Furthermore, the electric wire conductor 10 having a rectangularcross-section can provide a large space vertically (±y direction) andlaterally (±x direction), whereby the space-saving property is furtherimproved. Especially, in the case of assembling the plurality ofelectric wires with stacking one electric wire on another electric wire,or with aligning one electric wire laterally to another electric wire,spaces between the plurality of electric wires along the heightdirection y and the width direction x can be reduced.

As described above, the electric wire conductor 10 according to thepresent embodiment contains the wire strand containing a plurality ofelemental wires 1 twisted together, and the wire strand has a flat outershape. Therefore, the electric wire conductor 10 has excellentflexibility in each direction. Patent Literature 1 discloses arectangular conductor that has flexibility in the height direction to acertain degree, but shows low flexibility in the width direction and istoo rigid to bend easily in the width direction. In contrast, theelectric wire conductor 10 according to the present embodiment includingthe wire strand has the excellent flexibility and easily bends in thewidth direction x as well as the height direction y.

Thus, the electric wire conductor 10 according to the present embodimentcan achieve both the flexibility, which provides freedom in routing, andthe space-saving property. In an automobile, for example, due to recenthigh functionalization, the number of electric wires and components tobe disposed is increasing. Also, a larger electric current is demandedfor vehicles such as electric vehicles, which results in enlargement ofa diameter of the electric wire, whereby a space for routing individualelectric wires has been reduced. However, the electric wire conductor 10according to the present embodiment can effectively use a small spacewhen routed because of the space-saving property and the excellentflexibility. In the case of assembling a great number of electric wires,or using an electric wire having a large conductor cross-sectional area,this advantage is especially enhanced.

In the above-described embodiment, the electric wire conductor 10 has arectangular cross-section. However, as described above, thecross-section of the electric wire conductor 10 may be of any shape aslong as it is flat. FIGS. 4B to 4D show other examples of thecross-sectional shape. Here, in FIGS. 4B to 4D, the elemental wires 1are omitted to show only the outer shape of the cross-section, that is,a circumscribed edges which approximate cross-sections of the electricwire conductors. FIG. 4B shows a cross-section in an ellipse shape (ashape of a rectangle with half circles attached to both ends) . As across-section in a quadrangle shape other than the above-mentionedrectangular shape, FIG. 4C shows a cross-section in a trapezoidal shape,and FIG. 4D shows a cross-section in a parallelogram shape. Since theelectric wire conductor 10 has a quadrangle cross-section, a greatnumber of electric wire conductors 10 may be disposed in the heightdirection y and the width direction x with small spaces, whichcontributes to the excellent space-saving property for assembling agreat number of electric wires. This advantage is especially remarkablewhen the cross-sectional shape is a rectangle as described above.

(2) Vacancy in the Cross-Section of the Electric Wire Conductor

Further, the electric wire conductor 10 according to the presentembodiment has a vacancy ratio of 17% or higher at the cross-section ofthe flat portion. The vacancy ratio at the cross-section of the electricwire conductor 10 is defined as, within the cross-section of theelectric wire conductor 10 perpendicularly intersecting the axialdirection, a proportion of an area of vacancy not occupied by theelemental wires 1 to an entire area of the whole electric wire conductor10, that is, an area of a region surrounded by the outline of the entireelectric wire conductor 10.

As described above, the electric wire conductor 10 has high flexibilityboth in the height direction y and the width direction x because of itsflat shape, and it can easily bend. By having sufficient vacancy such asthe ratio of 17% or higher in the cross-section of the electric wireconductor 10, the elemental wires 1 can move in the electric wireconductor 10 using the vacancy when the electric wire conductor 10 bendsalong the height direction y or the width direction x, so that theelectric wire conductor 10 can bend more easily. Thus, the flexibilityof the electric wire conductor 10 is improved. For the purpose offurther improving the flexibility, the vacancy ratio is preferably 20%or higher, and more preferably 25% or higher.

An upper limit of the vacancy is not specifically determined; however,from the viewpoint of effectively forming the electric wire conductor 10into a flat shape by pressing, and effectively keeping the formed flatshape, the vacancy ratio is preferably 40% or lower, and more preferably35% or lower.

In the cross-section of the electric wire conductor 10, small vacanciesare provided in a region between each of the elemental wires 1. Thevacancy ratio as defined above is a ratio of the area of these smallvacancies in total with respect to the cross-sectional area of theelectric wire conductor 10. When the total area of these small vacanciesis equal to or more than the predetermined proportion in thecross-section of the electric wire conductor 10, the flexibility of theelectric wire conductor 10 is improved. In addition, sizes of therespective vacancies in the region between each of the elemental wires 1also contributes improvement in flexibility of the electric wireconductor 10. In other words, a state where vacancies of a certain sizeare provided in the cross-section of the electric wire conductor 10 as acontinuous region can improve the flexibility of the electric wireconductor 10 more effectively than a state where minute vacancies areevenly spread over the cross-section of the electric wire conductor 10.Specifically, the cross-section of the electric wire conductor 10preferably contains a continuous vacancy such that two or more,preferably three or more of the elemental wires 1 can be accommodatedtherein. This is because the elemental wires 1 moving into such a largevacancy enables flexible bending of the electric wire. Here, anelemental wire 1 used for judging whether the certain vacancy is capableof accommodating the elemental wire may be an elemental wire 1surrounding the vacancy, or an elemental wire having a circularcross-section with the same cross-sectional area as that of anyelemental wire 1 forming the electric wire conductor 10. For example, inFIG. 4A, a vacancy indicated by a reference sign v is capable ofaccommodating two or more of the elemental wires.

For evaluation of the cross-sectional area of the electric wireconductor 10 and the area of the vacancy, the electric wire conductor 10or the covered electric wire 20 having the insulator 21 on the outerperiphery the electric wire conductor 10 may be subjected to processessuch as cutting and polishing to obtain a cross-section, and then, sucha cross-section is photographed for measurement. In the preparation ofthe cross-section, the electric wire conductor 10 and the coveredelectric wire 20 may be embedded in transparent resin for example priorto the operation including cutting as appropriate, to prevent a changein the shape or the area of the vacancies due to the operation includingcutting. Further, the area of the electric wire conductor 10 and thearea of the vacancy may be evaluated for the entire cross-section of theelectric wire conductor 10, or alternatively, in order to eliminateinfluence of the irregular structure in an outermost periphery of theelectric wire conductor 10, the areas of the electric wire conductor 10and the vacancies may be evaluated for an inner region where theoutermost periphery of the electric wire conductor 10 is excluded,instead of evaluating the whole cross-section if the elemental wires 1are sufficient in number such as equals to or more than 50.

(3) Cross-Sectional Shape of Each Elemental Wire

For the electric wire conductor 10 according to the present embodiment,the cross-sectional shape of each elemental wire 1 constituting theelectric wire conductor 10 may be of any shape as long as the outershape of the entire electric wire conductor 10 is flat. A conventionalelectric wire having a substantially circular cross-section may beemployed as the elemental wire 1 in the present embodiment. However, atleast a part of the plurality of elemental wires 1 may havecross-sections of shapes deviated from a circle, such as flat shapes. Aswill be described later, when a raw wire strand 10′ is pressed into aflat shape, at least a part of the elemental wires 1 may be deformedinto flat shapes, depending on, for example, the material constitutingthe elemental wires 1.

For the electric wire conductor 10 according to the present embodiment,in the cross-section perpendicularly intersecting the axial direction,deformation ratios of the elemental wires 1 are lower at a peripheralpart facing the outer periphery of the electric wire conductor 10 thanat a center part which is located inside of the peripheral part. FIGS. 1and 2 schematically show distribution of the deformation ratio of suchelemental wires 1.

Here, the deformation ratio of an elemental wire 1 is an index showing adegree of deviation from a circle for a cross-section of a certainelemental wire 1. For an elemental wire 1 actually contained in theelectric wire conductor 10, a longest diameter A is defined as a lengthof the longest line laterally crossing the cross-section, and a diameterR is defined as a diameter of a circle having the same area as thecross-sectional area of the elemental wire 1. Then, a deformation ratioD of the elemental wire 1 is represented as follows:D=(A−R)/R×100%   Formula (1)

The diameter R may be obtained by measuring a cross-sectional area ofthe elemental wire 1, or alternatively, if a diameter of the elementalwire 1 before deformed such as as by pressing is known, or if a portionin which the elemental wires 1 are not deformed (corresponding to alow-flatness portion as will be described later) is also included in thesame electric wire conductor 10, a diameter of the elemental wire 1which is not deformed may be used as the diameter R. Further, onlyelemental wires 1 disposed on the outermost periphery of the electricwire conductor 10 may be employed as the elemental wires 1 in theperipheral part, and only elemental wires 1 disposed in the center ofthe electric wire conductor 10 may be employed as the elemental wires 1in the center part; however, from the viewpoint of reducing influence ofvariation in deformation of the elemental wires 1, the deformation ratioD is preferably obtained as an average value of a plurality of elementalwires 1 included in a region having a certain area. For example, regionssurrounded by a rectangle with edges in a length of approximately 10 to30% of the width W of the electric wire conductor 10, or regionssurrounded by a circle having a diameter of approximately 10 to 30% ofthe width W may be employed including the outermost periphery or thecenter of the electric wire conductor 10, and such regions may bedefined as the peripheral part and the center part, respectively.

The cross-section of the electric wire conductor 10 according to thepresent embodiment having a flat shape can be formed more efficiently ifthe elemental wires 1 located in the upper and lower direction (±ydirection) of the peripheral part of the electric wire conductor 10 aredeformed into flat shapes than in the case where the elemental wires 1located in the center part are deformed. However, if the elemental wires1 in the peripheral part are intensively deformed, loads areconcentrated on these elemental wires 1, whereby physical properties ofthe elemental wires 1 in the peripheral part of the electric wireconductor 10 become significantly different from those of the innerregion. Further, since the shape of the elemental wires 1 in theperipheral part, especially in the outermost periphery defines the outershape of the entire electric wire conductor 10, drastic deformation ofsuch elemental wires 1 possibly causes an unnecessary irregularstructure to be formed on the outer surface of the electric wireconductor 10. Such an irregular structure includes a sharp protrusion(i.e., burr) that may possibly be formed during processing of the rawwire strand 10′ into a flat shape. The burr tends to be formedespecially on end parts of the electric wire conductor 10 in the widthdirection (±x direction).

Meanwhile, in the electric wire conductor 10, making the deformationratio of the elemental wire 1 at the peripheral part smaller than thedeformation ratio of the elemental wire 1 at the center part can preventconcentration of the loads for deformation to the elemental wires 1 inthe peripheral part and the formation of the unnecessary irregularstructure on the outer periphery of the electric wire conductor 10. Asdescribed above, since the vacancy ratio of 17% or higher is ensured inthe electric wire conductor 10 according to the present embodiment, andthe elemental wires 1 may be arranged in various relative locationsbecause of presence of the vacancies between the elemental wires 1, thecross-section of the electric wire conductor 10 can be formed into adesired flat shape depending on the relative arrangement of theelemental wires 1, without drastic deformation of the shapes of eachelemental wires 1.

From the viewpoint of effectively preventing the concentration of theloads for deformation to the elemental wires 1 at the peripheral part ofthe electric wire conductor 10 and the formation of the unnecessaryirregular structure on the surface of the electric wire conductor 10, aratio of the deformation ratio of elemental wire 1 at the peripheralpart to the deformation ratio of elemental wire 1 at the center part(i.e., peripheral deformation ratio ; deformation ratio at theperipheral part/deformation ratio at the center part×100%) is preferably70% or lower, more preferably 50% or lower, and still more preferably25% or lower. In addition, a value of the deformation ratio of theelemental wire 1 at the peripheral part is preferably 10% or lower, andmore preferably 5% or lower. It is preferable that the deformation ratioof the elemental wire 1 at the peripheral part is as small as possible,and the lower limit of the deformation ratio is not particularlyspecified.

The deformation ratio of the elemental wire 1 in the center part is notspecifically limited; however, from the viewpoint of preventingapplication of loads to the elemental wire 1 due to excessivedeformation, the deformation ratio of the elemental wire 1 in the centerpart is preferably 50% or lower, and more preferably 30% or lower. Onthe other hand, from the viewpoint of effectively forming thecross-section of the electric wire conductor 10 to have the flat shapewhile suppressing the deformation of the elemental wire 1 in theperipheral part, the deformation ratio at the center part is preferably10% or higher, and more preferably 20% or higher.

When the cross-section of the electric wire conductor 10 containsopposing edges 11 and 12 parallel to the width direction x, especially,when the cross-section of the electric wire conductor 10 has arectangular shape, it is preferable that the deformation ratios of theelemental wires 1 at end parts in the width direction of thecross-section, that is, at both end parts of the parallel opposing edges11 and 12 are kept particularly low. This is because, when thecross-section of the electric wire conductor 10 is formed into such ashape, in order to form the parallel opposing edges 11 and 12 along thewidth direction x, and to form a corner structure of an approximatelyright angle, the deformation ratio at the end parts in the widthdirection tends to be high. Further, processes for formation of theelectric wire conductor 10 such as compression of the raw wire strand10′ possibly causes sharp burrs in the end parts. From the viewpoint ofpreventing those phenomena, in the cross-section of the electric wireconductor 10, the deformation ratios of the elemental wires 1particularly at the end parts in the peripheral part are preferably 70%or lower, more preferably 50% or lower, and still more preferably 25% orlower of the deformation ratios of the elemental wires 1 at the centerpart. In addition, a value of the deformation ratios of the elementalwires 1 at the end parts is preferably 10% or lower, more preferably 5%or lower. Further, when the deformation ratios of the elemental wires 1are compared within the peripheral part between the end parts and theside parts, it is preferable that the deformation ratio at the end partsis lower than the deformation ratio at the side parts, where the sideparts mean intermediate parts of the opposing edges 11 and 12 along thewidth x direction excepting the end parts. In other words, thedeformation ratios are preferably in the following order, from thelowest: the end part, the side part, and the center part.

In the electric wire conductor 10, as the number of the elemental wire 1is increased, it becomes easier to form the cross-section into a flatshape while keeping the deformation ratios of the elemental wires 1 atthe peripheral part lower than those at the center part and maintainingthe high vacancy ratio such as 17% or higher. For example, when thenumber of the element wire 1 is 50 or more, the condition as above canbe sufficiently achieved owing to variation in relative arrangements ofthe elemental wires 1. On the other hand, when the number of theelemental wire 1 is less than 50, it is still preferable to ensure thevacancy ratio of 17% or higher for the purpose of obtaining thesufficient flexibility of the electric wire conductor 10, even if theelemental wires 1 in the peripheral part are deformed at a deformationratio equivalent to or higher than the elemental wires 1 in the centerpart.

(4) Material and Conductor Cross-Sectional Area of the Electric WireConductor

The elemental wires 1 constituting the electric wire conductor 10 may bemade of any conductive material such as a metal material. Examples oftypical material constituting the elemental wire 1 may contain copper, acopper alloy, aluminum, and an aluminum alloy. These metal materials aresuitable for the electric wire conductor 10 according to the presentembodiment in that processes of forming the wire strand and pressinginto a flat shape are easy to be carried out, and the flat shape is easyto be maintained. As the elemental wires 1 constituting the electricwire conductor 10, the elemental wires all made of the same material maybe used, or a multiple kinds of elemental wires made of differentmaterials may be mixed.

The conductor cross-sectional area of the electric wire conductor 10maybe appropriately selected according to a desired electricalconductivity, for example. However, the larger the conductorcross-sectional area is, the easier it becomes to form the flat shape byprocesses such as pressing, and the flat shape once formed can be firmlymaintained. From such a viewpoint, preferable conductor cross-sectionalarea is, for example, 16 mm² or more when the elemental wires 1constituting the electric wire conductor 10 are made of copper or acopper alloy, and 40 mm² or more when the elemental wires 1 are made ofaluminum or an aluminum alloy.

Further, in a case where the conductor cross-sectional area is as largeas 100 mm² or more, if the electric wire conductor has a substantiallycircular cross-section, a diameter of the circular cross-section becomeslarge so that a large space is required for routing, and an opposingforce incurred upon bending becomes large, whereby it becomes difficultto ensure the flexibility sufficient for routing. In contrast, theelectric wire conductor 10 having the flat cross-section enables theheight H to be kept smaller than in the case of the electric wireconductor having the substantially circular cross-section with the sameconductor cross-sectional area. Thus, a space in the height direction yoccupied by the electric wire conductor 10 is reduced, the opposingforce generated upon bending along the height direction y becomessmaller, whereby the flexibility required for routing is efficientlyachieved. Also, by forming the cross-sectional shape of the electricwire conductor 10 with a large conductor cross-sectional area into flat,a heat dissipation performance of the electric wire conductor 10 isenhanced. From the viewpoint of effectively utilizing these advantagessuch as ensuring the flexibility, the conductor cross-sectional area ispreferably 100 mm² or larger when the electric wire conductor 10 is madeof copper or a copper alloy. The conductor cross-sectional area ispreferably 130 mm² or larger when the electric wire conductor 10 is madeof aluminum or an aluminum alloy. The electric wire conductor 10 havingsuch a large conductor cross-sectional area is anticipated forapplication to a power supply wire for an electric vehicle of highoutput, for example. Since the power supply wires are required to berouted in a limited space in the vehicle, the space-saving property andflexibility of the electric wire conductor 10 having a flatcross-section are advantageous. In particular, from the viewpoint ofreducing vehicle weight, it is effective to form the electric wireconductor 10 having a large conductor cross-sectional area from aluminumor an aluminum alloy; however, since aluminum and an aluminum alloy havea lower electrical conductivity than copper and a copper alloy, theelectric wire conductor 10 having a particularly large conductorcross-sectional area such as 130 mm² or more is needed for obtaining therequired electrical conductivity.

Furthermore, preferable outer diameter of each elemental wire 1contained in the electric wire conductor 10 is 0.3 to 1.0mm, forexample. The number of elemental wires 1 contained in the electric wireconductor 10 is determined depending on the conductor cross-sectionalarea of the electric wire conductor 10 and the outer diameter of theelemental wires 1 to be used. Meanwhile, as the number of elementalwires 1 is increased, the elemental wires 1 may be disposed in morevarious relative positions, which makes it easier to form the electricwire conductor 10 to have the flat cross-section while ensuring the highvacancy ratio of 17% or higher, and further keeping the deformationratio of the elemental wires 1 at the peripheral part of the electricwire conductor 10 low. From this viewpoint, the number of elementalwires 1 is preferably 50 or more, more preferably 100 or more, and stillmore preferably 500 or more.

(5) Aspect Ratio of the Electric Wire Conductor

For the cross-section of the electric wire conductor 10, an aspect ratio(H:W) of the flat shape may be appropriately selected in considerationof a desired space-saving property, for example. The range of 1:2 to 1:8may be provided as an example of the aspect ratio. Within this range,the wire strand can be effectively formed into the flat shape whileobtaining the high space-saving property. Further, in a case where theelectric wire conductor 10 is used for wiring in an automobile, forexample, a configuration in which a height H is 3 mm or smaller may beprovided as a preferable example.

As will be described later, when a raw wire strand 10′ formed of aconventional wire strand having a substantially circular cross-sectionis subjected to pressing to form the electric wire conductor 10 having aflat cross-section, vacancies between the elemental wires 1 tend to besmaller as the rolling process proceeds. Especially, the higher theaspect ratio of the flat cross-section of the electric wire conductor 10is (the width W is larger in comparison with the height H) , the lowerthe vacancy ratio tends to be. However, when the vacancy ratio of 17% orhigher as described above is ensured in the case where the aspect ratio(H:W) is 1:3 or higher, that is, the width W of the electric wireconductor 10 is three times or more larger than the height H, forexample, the electric wire conductor 10 can effectively achieve both thehigh space-saving property and the flexibility.

Further, by forming the electric wire conductor 10 to have a flatcross-section, a surface area becomes large compared with thesubstantially circular cross-section, which enhances the heatdissipation performance of the electric wire conductor 10. As a result,when a same amount of electrical current is applied, a temperature riseof the electric wire conductor 10 having a flat cross-section is smallerthan in the case where the conductor has a circular cross-section. Inother words, when an upper limit of temperature rise is determined, asame amount of electrical current can be applied to the electric wireconductor 10 having a flat cross-section with a conductorcross-sectional area smaller than that having a substantially circularcross-section, while suppressing the temperature rise within a rangebelow the upper limit. As the aspect ratio of the electric wireconductor 10 is increased, an effect of improving the heat dissipationperformance is enhanced. For example, as will be described in Examplesbelow, when the aspect ratio is 1:3 or higher, even if the conductorcross-sectional area of the electric wire conductor 10 having a flatcross-section is 90% of that of the electric wire conductor 10 having anapproximately circular cross-section, the temperature rise can besuppressed to the same degree. Further, the aspect ratio is preferably1:5 or higher.

(6) Other Embodiments

Hereinbefore, the embodiment has been described in which the entireregion of the electric wire conductor 10 in the axial direction consistsof the flat portion having a flat cross-section. However, the flatportion may constitute apart of the entire region in the axial directionof the electric wire conductor 10. That is to say, the flat portion anda low-flatness portion having a flatness (i.e., a ratio of W to H) lowerthan the flat portion may be arranged adjacent to each other along theaxial direction of the electric wire conductor 10, for example. The flatportion and the low-flatness portion consist of common elemental wires 1integrally continuous therethrough, and have different cross-sectionalshapes. The low-flatness portion has a cross-section approximatelycircular having a flatness of substantially one. By disposing the flatportion and the low-flatness portion continuously in one electric wireconductor 10, the electric wire conductor 10 can obtain both propertiesprovided by the flat portion and the low-flatness portion withoutprocess such as joining.

At the low-flatness portion, since the flatness of the electric wireconductor 10 obtained through process such as pressing is small, it ispreferable that the deformation ratio of the elemental wire 1 is smallerthan that in the flat portion, accordingly. In particular, in thelow-flatness portion having a substantially circular cross-section withthe flatness of substantially one, it is preferable that the elementalwires 1 also have substantially circular cross-sections.

The flat portion and the low-flatness portion may be disposed along theaxial direction of the electric wire conductor 10 in any order. However,a configuration in which the flat portion is disposed in the center partof the axial direction and the low-flatness portions having asubstantially circular cross-section are disposed on both ends thereofcan be presented as a preferred example. In this case, the flat portioncan be used for routing in a limited space, and simultaneously othermembers such as terminals are attached to both ends of the low-flatnessportions. Thus, it is possible to utilize both the space-saving propertyand the flexibility of the flat portion, as well as convenience ofattaching the other members to the low-flatness portions having acircular or substantially circular cross-section. Further, in the flatportion, a plurality of portions with different flatness may be disposedadjacent to each other.

[Production Method of Electric Wire Conductor]

As shown in FIG. 3 , the electric wire conductor 10 according to thepresent embodiment can be formed by pressing a raw wire strand 10′ whichcontains a plurality of elemental wires 1 twisted together and has asubstantially circular cross-section. For pressing, forces F1 and F2 areapplied from a first direction and a second direction opposing oneanother that are perpendicular to the axial direction of the raw wirestrand 10′ to compress the raw wire strand 10′, so as to obtain a flatelectric wire conductor 10 in which an applying direction of the forcesF1 and F2 corresponds to the height direction y.

Further, in addition to the forces F1 and F2 applied from the firstdirection and the second direction, forces F3 and F4 are applied to theraw wire strand 10′ from a third direction and a forth directionopposing one another and intersecting the first and second directions,so as to effectively form electric wire conductor 10 to have aquadrangular cross-section. Especially, by applying the forces F3 and F4from directions perpendicular to the forces F1 and F2, the electric wireconductor 10 is effectively formed to have a rectangular cross-section.In this case, by making the forces F1 and F2 larger than the forces F3and F4, the electric wire conductor 10 with a high flatness (i.e., theratio of W to H is large) can be obtained. Further, the forces F1 andF2, and the forces F3 and F4 may be applied simultaneously; however, byapplying the forces F1 and F2 first, and then applying the forces F1′and F2′ from the same directions as the forces F1 and F2 simultaneouslywith the forces F3 and F4, the electric wire conductor 10 with the highflatness can be obtained, in which the cross-section is firmly formedinto a quadrangular shape (especially, a rectangular shape). In the caseof changing the flatness along the axial direction of the electric wireconductor 10, the applied forces may be changed during the pressingalong the axial direction.

The forces may be applied to the raw wire strand 10′, for example, bypassing the raw wire strand 10′ between the rollers disposed opposing toeach other. The raw wire strand 10′ is pressed with the rollers whileextruded along a rolling direction of the rollers, whereby it ispossible to sufficiently deform the outer shape of the entire raw wirestrand 10′ into a flat shape without applying a heavy load to the rawwire strand 10′, compared with drawing where a die is used to compressthe raw wire strand 10′ or pressing where a press machine is used tocompress the raw wire strand 10′. Further, it is easier to apply a loadevenly over the entire raw wire strand 10′ without concentrating a highload to a peripheral part of the raw wire strand 10′ in contact with therollers. As a result, by using the rollers for the pressing of the rawwire strand 10′ , vacancies between the elemental wires 1 can besufficiently ensured in the flat cross-section of the electric wireconductor 10 thus obtained, compared with a case where a die or apressing machine is used. Further, the deformation ratio of each of theelemental wires 1 including the elemental wire 1 located in theperipheral part of the electric wire conductor 10 can be kept low. Thevacancy ratio and the deformation ratio of each of the elemental wires 1may be adjusted by changing the magnitude of applying forces for thepressing (F1, F2, F3, F4, F1′, and F2′) and a shape of a part of theroller contacting the raw wire strand 10′.

By using the rollers, the raw wire strand 10′ as a whole can be formedinto a flat shape while the deformation ratios of the elemental wires 1are suppressed, whereby change in physical properties of the producedelectrical wire conductor 10 due to the deformation of the elementalwires 1 can be suppressed. Thus, in many cases, a process such as heattreatment for eliminating influence of processing distortion or workhardening is not particularly required for the electric wire conductor10 after the rolling.

[Covered Electric Wire]

As described above, a covered electric wire 20 according to oneembodiment of the present invention contains the electric wire conductor10 according to the embodiment of the present invention as describedabove, and the insulator 21 which covers the outer periphery of theelectric wire conductor 10 (see FIGS. 5A and 5B, etc.).

An outer shape of the entire covered electric wire 20 including theinsulator 21 reflects the outer shape of the electric wire conductor 10.As the electric wire conductor 10 has a flat shape, the covered electricwire 20 also has a flat shape. Further, as the electric wire conductor10 has high flexibility in each direction, the covered electric wire 20also has high flexibility in each direction.

A material of the insulator 21 is not specifically limited, and avariety of polymer materials may be used to form the insulator 21.Further, the polymer material may contain fillers or additives asappropriate. However, it is preferable to select the material for theinsulator 21 and a thickness thereof such that the flexibility of theinsulator 21 is higher than the flexibility of the electric wireconductor 10, so as not to deteriorate the excellent flexibility of theelectric wire conductor 10. In addition, it is preferable to select thethickness of the insulator 21 such that the flat shape of the electricwire conductor 10 is sufficiently reflected to the shape of the entirecovered electric wire 20 so that the entire covered electric wire 20 hasa flat cross-section.

The insulator 21 may cover a whole periphery of the electric wireconductor 10. In this case, the insulator 21 can be provided byextruding the polymer material for the insulator 21 on the wholeperiphery of the electric wire conductor 10. Alternatively, sheet-shapedinsulators 21 may sandwich the electric wire conductor 10 from the topand the bottom in the height direction (±y direction) of the electricwire conductor 10. In this case, the polymer material formed into twosheets are disposed at the top and bottom of the electric wire conductor10 and may be adjoined each other by fusing or adhesion, for example, asappropriate.

The covered electric wire 20 may be used in a form of a single wire inwhich the outer periphery of one electric wire conductor 10 is coveredwith the insulator 21, or may be used in a form of a wiring harness inwhich a plurality of covered electric wires are assembled and integrallybundled with a covering material, for example, as necessary.Hereinafter, examples of the wiring harness containing the coveredelectric wires 20 will be described.

[Wiring Harness]

A wiring harness according to one embodiment of the present inventioncontains a plurality of covered electric wires being assembled, in whichat least a part of the plurality of covered electric wires are thecovered electric wires 20 according to the embodiment of the presentinvention containing the above-mentioned flat electric wire conductors10. The wiring harness may contain only the covered electric wires 20containing the above-mentioned flat electric wire conductors 10, or maycontain such covered electric wires 20 together with different kinds ofcovered electric wires such as a covered electric wire containing aconventional electric wire conductor having a substantially circularcross-section. Further, in a case where the wiring harness contains aplurality of covered electric wires 20 containing the flat electric wireconductors 10, features such as a material, shape, and size of theelectric wire conductor 10 and the insulator 21 constituting theplurality of the covered electric wires 20 may be of the same or may bedifferent from each other. The plurality of covered electric wirecontained in the wiring harness may be integrally bundled with aninsulation material, for example, as necessary.

(1) Arrangement of the Covered Electric Wires in Wiring Harness

In the case of constructing a wiring harness with the plurality ofcovered electric wires 20 containing the flat electric wire conductors10, the plurality of covered electric wires 20 may be disposed in anypositional relationship. For example, the covered electric wires 20 maybe aligned side by side in the width direction x (the lateral direction)of the flat electric wire conductor 10 as shown in FIG. 5A, or may bestacked in the height direction y as shown in FIG. 5B, or may be in amatrix shape in which the plurality of covered electric wires 20disposed side by side in the width direction x are stacked in multiplelayers in the height direction y (see FIG. 7B) . That is to say, theplurality of covered electric wires 20 may be aligned along at leasteither the width direction x or the height direction y. In this way, theneat arrangement of the plurality of covered electric wire 20 containingthe flat electric wire conductors 10 makes it possible to reduce spacesbetween the covered electric wires 20 forming the wiring harness, thusproviding the wiring harness with a remarkably excellent space-savingproperty.

In particular, in the case of disposing the plurality of coveredelectric wires 20 side by side in the width direction x of the flatelectric wire conductor 10, the space-saving property along the heightdirection y resulting from the flat shape of the electric wireconductors 10 may be effectively used in formation and routing of thewiring harness. The space-saving property can be effectively used, forexample, when the wiring harness is routed in a space of a limitedheight, or when other member is disposed above or below the wiringharness. Further, the heat dissipation performance of each of thecovered electric wires 20 can be effectively achieved.

On the other hand, in the case where the plurality of covered electricwires 20 are arranged in the height direction y of the flat electricwire conductor 10, that is, stacked in multiple layers along the heightdirection y, the wiring harness can be constructed and routed whilekeeping a size in the width direction x of the entire wiring harnesssmall even when a size in the width direction x (the width W) of theelectric wire conductor 10 is large due to its flat shape. As a result,a space such as a long and thin space in the height direction can beutilized for routing.

In the wiring harness, disposing a heat dissipation sheet in contactwith each of the aligned covered electric wires 20 makes it possible toensure the heat dissipation performance of each of the covered electricwires 20, even when a great number of the covered electric wires 20 arealigned closely to one another by utilizing the flat shape. Here, theheat dissipation sheet is a sheet-shaped (including plate-shaped) memberconsisting of a heat dissipation material having a heat dissipationperformance higher than the covered electric wire 20. Examples of theheat dissipation sheet may include a sheet or a plate made of aluminumor an aluminum alloy. For example, the heat dissipation sheet may bedisposed between the plurality of covered electric wires 20 constitutingthe wiring harness, or disposed commonly contacting the plurality ofcovered electric wires 20.

As shown in FIG. 5A, in the case of aligning the plurality of coveredelectric wires 20 side by side in the width direction x, a heatdissipation sheet 31 is preferably disposed so as to commonly contactthe surfaces of the covered electric wires 20 along the width directionx (a flat surface) . When the flat surface having a large area resultingfrom the flat shape of the electric wire conductor 10 is in contact witha surface on one side of the heat dissipation sheet, the heatdissipation performance of the covered electric wire 20 can beeffectively enhanced. Further, by commonly arranging the heatdissipation sheet 31 for the plurality of covered electric wires 20, theconfiguration of the wiring harness containing the heat dissipationsheet 31 can be simple. In the configuration illustrated in the figure,the covered electric wires 20 are not in contact with each other in thewidth direction x; however, when they contact with each other, it ispreferable that the heat dissipation sheets are also interposed betweenthe covered electric wires 20 adjacent to each other.

As shown in FIG. 5B, in the case of aligning the plurality of coveredelectric wires 20 in the height direction y, it is preferable to disposea heat dissipation sheet as an interposing sheet 32 to be disposedbetween each of the covered electric wires 20. The interposing sheets 32are in contact with flat surfaces of the respective covered electricwires 20 along the width direction x. As the flat surface has a largearea because of the flat shape of the electric wire conductor 10, ittends to be difficult to outwardly dissipate heat generated byapplication of an electric current in the alignment where the pluralityof the covered electric wire 20 are disposed with the flat surfaces withlarge area close to or in contact with each other; however, theinterposing sheet 32 between the covered electric wires 20 promotes heatdissipation.

Further, the plurality of interposing sheets 32 disposed between therespective covered electric wires 20 are preferably connected with oneanother by a connection member 33 made of a heat dissipation material.The connection member 33 enhances the heat dissipation performance ofeach of the covered electric wires 20, compared with the case where onlythe interposing sheets 32 are disposed. The connection member 33 may bedisposed as a member specialized in heat dissipation of the coveredelectric wires 20 via the interposing sheets 32, or a member which isdisposed for another purpose. For example, a columnar memberconstituting an automobile body may be used as the connection member 33so that the member may serve as a structure material for the automobilebody, as the connection member 33 which helps the heat dissipation ofthe covered electric wires 20 via the interposing sheets 32, and furtheras a support member for supporting the wiring harness containing theplurality of covered electric wires 20.

As will be described in the Examples below, when the heat dissipationsheet 31 made of aluminum or an aluminum alloy is disposed in contactwith the flat surface of the covered electric wire 20 along the widthdirection x as shown in FIG. 5A, a cross-sectional area at across-section of the heat dissipation sheet 31 perpendicularlyintersecting the axial direction of the covered electric wire 20 is, forevery covered electric wire, preferably 1.5 times or larger, and morepreferably 4 times or larger of the cross-sectional area of the electricwire conductor 10 constituting the covered electric wire 20. Then, theheat dissipation performance of the covered electric wire 20 can beeffectively enhanced.

(2) Routing in an Automobile

As described above, when the wiring harness including the coveredelectric wires 20 having the flat electric wire conductor 10 is used,for example, as a wiring material for an automobile, it is possible toeffectively utilize the excellent space-saving property. Routing such awiring harness along a member such as floor and a frame of a vehiclemakes it possible to effectively utilize a limited space under the flooror around the frame for routing. Meanwhile, when the wiring harness isdisposed such that the width direction x of the electric wire conductor10 is approximately parallel to the surface of a floor or a framemember, more excellent space-saving property can be achieved.

A conventional wiring harness contains covered electric wires having asubstantially circular cross-section bundled together, thus the entirewiring harness tends to be bulky. In order to produce a space forrouting in an automobile, a residential space (a space where a passengercan stay) is often reduced. However, as described above, when the wiringharness containing the covered electric wires 20 containing the flatelectric wire conductor 10 is used to keep the space necessary forrouting the wiring harness small, a large residential space can beprovided.

The wiring harness according to the present embodiment may be used in anautomobile as a wiring material for any purpose; and for example, it maybe used as a power-supply trunk line to be disposed under a floor. Aconventional power-supply trunk line for an automobile has been made ofa material which contains an insulation sheet and copper plates disposedside by side; however, continuously forming a large copper plate isdifficult and results in a low productivity. In addition, since thematerial contains a continuous metal body, fatigue fracture of thematerial possibly occurs due to influence of engine vibration of theautomobile, for example. In contrast, when the wiring harness accordingto the present embodiment constitutes a power-supply trunk wire, each ofthe process of forming the elemental wire 1 constituting the electricwire conductor 10, twisting the elemental wires 1, and forming the rawwire strand 10′ obtained through twisting of the elemental wires 1 intoa flat shape can be continuously performed for every portion of acontinuous material, thus achieving a high productivity. Further, as theelectric wire conductor 10 contains thin elemental wires 1, the entireelectric wire conductor 10 has a high durability against bending andvibration. Therefore, the fatigue fracture due to the engine vibration,for example, hardly occurs.

The wiring harness may not only be routed under the floor of theautomobile, but also form a floor or a ceiling itself with the wiringharness according to the present embodiment, for example. In anautomobile, the wiring harness needs to be routed so as not to interferewith components such as an engine; however, such a wiring route islimited. In particular, in an automobile requiring a large current suchas a hybrid vehicle and an electric vehicle, an electric wire with alarge conductor cross-sectional area is required to be routed, but awiring route capable of arranging the wiring harness including such anelectric wire with a large conductor cross-sectional area is limited.However, by constituting the floor or the ceiling with the wiringharness according to the present embodiment, the space can effectivelyprovide the wiring route, and also a large residential space can beensured, which leads to both the space-saving property and therequirement for application of a large electric current. Further, in acovered electric wire for a large electric current, an insulator easilydeteriorates due to a heat generated by an electric wire conductor;however, arranging the wiring harness as the floor and the ceiling caneffectively enhance heat dissipation performance. As a result, althoughan insulator 21 of low price with a comparatively low heat dissipationperformance is used to configure the covered electric wire 20,deterioration of the insulator 21 hardly occurs. Furthermore, as thecovered electric wire 20 containing the flat electric wire conductor 10has the flat surface, the covered electric wires 20 may be disposed invarious arrangements within a wiring harness, so that a combination ofthe flat surfaces enables the floor and the ceiling to have any surfaceshapes. When the wiring harness according to the present embodimentconstitutes the floor or the ceiling, a covering material may beappropriately arranged on the outer side of the wiring harness so as notto directly expose the wiring harness to a ceiling surface and a floorsurface.

Moreover, when the wiring harness according to the present embodiment isdisposed on the ceiling and the floor of the automobile, the pluralityof covered electric wires 20 forming the wiring harness are preferablyof a uniform height H as shown in FIG. 6 although they have differentconductor cross-sectional areas. Accordingly, upper and lower surfacesin the height direction of the wiring harness may be configured flat,whereby a high space-saving property is achieved in the height directionwhen the wiring harness is routed along the ceiling surface and thefloor surface. Also, an irregular structure in the height direction ofthe wiring harness hardly affects interior design of the automobile orfunctions of adjacent members. Here, the concept that “the coveredelectric wires 20 are of the uniform height H” refers to a state wheredifferences of the height H among the individual covered electric wires20 are within 10% of the average height.

As shown in FIG. 6 , it is preferable that the wiring harness in whichthe height H of the covered electric wires 20 are uniform as describedabove is disposed , for example, between an interior member 51 formingthe floor or the ceiling of the automobile and a sound absorbing member52 disposed adjacent to an outer side of the interior member 51 (on anopposite side of the residential space) such that the flat surfaces ofthe wiring harness along the width direction x are disposed alongsurfaces of the interior member 51 and the sound absorbing member 52.Then, a small space between the interior member 51 and the soundabsorbing member 52 can be effectively utilized for routing the wiringharness . As the height H of the covered electric wires 20 is uniform,the wiring harness can be arranged without unnecessarily increasing adistance between the interior member 51 and the sound absorbing member52. Further, a possible problem may be prevented where an irregularstructure in the height direction of the wiring harness appears as anirregular structure on the surface of the interior member 51 todeteriorate a surface design of the interior member 51. Furthermore,another possible problem may be prevented where the covered electricwires 20 with a large and non-uniform height H press the surface of thesound absorbing member 52 to affect a performance of the sound absorbingmember 52, including nonuniformity in a sound absorbing property. Here,examples of a combination of the interior member 51 and the soundabsorbing member 52 may include a combination of a floor carpet and asilencer.

Moreover, the wiring harness according to the present embodiment may berouted in the automobile while using a variety of members constitutingthe automobile body as a supporting member. For example, as shown inFIG. 7A, the wiring harness may be disposed along an outer periphery ofa columnar member constituting the automobile body. The wiring harnessmay be disposed so that a surface along the width direction x of each ofthe covered electric wires 20 forming the wiring harness is arrangedalong an outer peripheral surface of the columnar member 41.Alternatively, as shown in FIG. 7B, the wiring harness may be disposedin a continuous member having a cross-section intersecting thelongitudinal direction in a substantially U-shape or a channel shape, inother words, the wiring harness may be disposed in a hollow part 42 b ofa hollow tubular member 42 having an opening 42 a along the longitudinaldirection. The wiring harness may be configured in which the pluralityof covered electric wires 20 are aligned in the width x direction and/orthe height y direction in accordance with shapes of the opening 42 a andthe hollow part 42 b. As described above, the heat dissipation sheetsmay be disposed as appropriate between the aligned covered electricwires 20. Examples of the columnar member 41 and the tubular member 42include a member used as a reinforcement which is disposed in a frontside of an instrument panel of automobiles.

(3) Combination with Other Electric Wires

As described above, the wiring harness according to an embodiment of thepresent invention may contain the covered electric wires 20 containingthe flat electric wire conductor 10 according to an embodiment of thepresent invention in combination with other kinds of covered electricwires. The covered electric wires 20 according to an embodiment of thepresent invention and other kinds of covered electric wires may havecombination of specific features such as constituent material, shape,and size. Among them, examples may include a configuration using thecovered electric wire conductor 20 according to an embodiment of thepresent invention (i.e., a first covered electric wire) containing theflat electric wire conductor 10 made of aluminum or an aluminum alloy(i.e., aluminum material), and other kinds of covered electric wire(i.e., a second covered electric wire) containing an electric wireconductor made of copper or a copper alloy (i.e., copper material)having a substantially circular cross-section, for example, with theflatness lower than the electric wire conductor 10 of the first coveredelectric wire 20. In this case, it is preferable that a conductorcross-sectional area of the second covered electric wire is smaller thana conductor cross-sectional area of the first covered electric wire 20.

The aluminum material has come to be used as an electric wire conductivematerial for automobiles instead of the copper material for the purposeof reducing automobile weight; however, as described above, in the casewhere the aluminum material is used, the conductor cross-sectional areaof the electric wire conductor tends to be larger than in the case wherethe copper material is used, because the aluminum material has a lowerelectrical conductivity as a material. Thus, if the electric wireconductor made of an aluminum material is used as a conventionalconductor having a circular cross-section and contained in the wiringharness, a diameter of the electric wire conductor becomes large, whichrequires a large space for routing the wiring harness; however, the flatelectric wire conductor 10 can reduce the space required for routingwhile ensuring the large conductor cross-sectional area. On the otherhand, even the electric wire conductor made of the copper material isused, it does not significantly interfere the weight reduction ofautomobiles as long as it is a small diameter wire with a smallconductor cross-sectional area. Also, it hardly enlarges space requiredfor routing the wiring harness. Accordingly, using the first coveredelectric wire 20 including the flat electric wire conductor 10 made ofthe aluminum material in combination with the second covered electricwire including the electric wire conductor having a substantiallycircular cross-section made of the copper material with a smallerconductor cross-sectional area, excellent properties of the coppermaterial such as a high electrical conductivity may be utilized as aproperty of a part of the wiring harness while ensuring the space-savingproperty. Suitable examples of the electric wire conductor constitutingthe second covered electric wire may include a copper alloy thin wirewith a conductor cross-sectional area of 0.13 mm² or smaller. Such acopper alloy thin wire may be suitably used as a signal wire. Formingthe second covered electric wire into thin as described above makes itpossible to effectively utilize the space-saving property brought aboutby the flat electric wire conductor 10 contained in the first coveredelectric wire 20.

EXAMPLE

Hereinafter, examples according to an embodiment of the presentinvention are explained. It should be noted that the present inventionis not limited by these examples.

[State of Cross-Section of Electric Wire Conductor]

For a cross-section of an electric wire conductor formed into flat,state of vacancies and state of deformation of elemental wires wereinvestigated.

(Test Method)

A raw wire strand having a substantially circular cross-sectional shapehaving a conductor cross-sectional area of 60 mm² was prepared bytwisting 741 aluminum alloy wires having an outer diameter of 0.32 mm.

The raw wire strand was subjected to pressing with rollers to prepare anelectric wire conductor having a substantially rectangularcross-section. The pressing with the roller was carried out, as shown inFIG. 3 , by firstly applying forces F1 and F2 from upper and lowerdirections, then applying forces F1′ and F2′ again from the samedirections, and simultaneously applying forces F3 and F4 from both sidesof a width direction. In this process, the applying forces were variedbetween samples to prepare Sample 1 with a low compression rate(reduction rate of a cross-sectional area) while Sample 2 with a highcompression rate. Then, an outer periphery of each of the electric wireconductors was covered with an insulator containing polyvinyl chloride(PVC) having a thickness of 1.5 mm.

Each of Sample 1 and Sample 2 was embedded in an epoxy-based resin, anda cross-section intersecting an axial direction was polished to preparea cross-sectional sample. Then, the obtained cross-sectional sampleswere photographed.

Photographic images of the cross-sections were subjected to imageanalysis to evaluate vacancy ratios. In the analysis, a cross-sectionalarea of the entire electric wire conductor (A0) was estimated from anarea of a region inside an outline connecting outlines of elementalwires located at an outermost periphery of the electric wire conductor,and within the above-described region, an area of vacancies (A1) wasestimated from an area of a region that was not occupied by theelemental wires. A vacancy ratio (A1/A0×100%) was calculated.

Further, by the image analysis, deformation ratios of the elemental wirewere evaluated. For evaluation, the deformation ratios of the elementalwires were estimated in accordance with Formula (1) as provided above.As a diameter R, the outer diameter of 0.32 mm of the raw wire strandbefore compressed was employed. The deformation ratios of the elementalwires were estimated for elemental wires included in a peripheral part(end part) which is shown as square region R1, and for elemental wiresincluded in a center part which is shown as square region R2 in FIGS. 8Band 8C. An average value of the deformation ratio at each region wascalculated. Further, a ratio of the deformation ratio at the peripheralpart to the deformation ratio at the center part was calculated as aperipheral deformation ratio (i.e., deformation ratio at the peripheralpart/deformation ratio at the center part×100%).

(Test Results)

FIGS. 8A to 8C are photographic images of the cross-sections of thecovered electric wires. FIG. 8A shows a raw wire strand beforecompression, FIG. 8B shows Sample 1 with a low compression rate, andFIG. 8C shows Sample 2 with a high compression rate. Further, Table 1below shows values of vacancy ratio and deformation ratio of Samples 1and 2 obtained through image analysis.

TABLE 1 Deformation Ratio of Elemental Wires Vacancy Peripheral CenterPeripheral Ratio part part deformation ratio Sample 1 30% 3.8% 21%  18%Sample 2 16%  21% 21% 100%

Comparing the cross-sectional images of Sample 1 and Sample 2 in FIGS.8B and 8C, Sample 1 had comparatively large vacancies between theelemental wires, while Sample 2 included the elemental wires denselyfilled. In addition, while the cross-section of each elemental wire inSample 1 was not significantly deformed from a substantially circularshape before pressed shown in FIG. 8A, many elemental wires in Sample 2were significantly deformed from a circle. In particular, focusing onthe end part in the width direction of the electric wire conductor,while the end portion was formed smoothly in Sample 1, a sharp burr wasproduced in Sample 2 as indicated by a circle.

These features observed in the photographic images were more obviouslyshown by the results of the image analysis in Table 1. First, thevacancy ratio in the cross-section of the electric wire conductor was30% in Sample 1 and 16% in Sample 2. The value of Sample 1 was two timeslarger than that of Sample 2. In addition, in Sample 1, as pointed by anarrow in FIG. 8B, many continuous vacancies capable of accommodating twoor more of elemental wires were present. On the other hand, such largecontinuous vacancies were hardly found in Sample 2 as shown in FIG. 8C.

Next, regarding the deformations ratio of the elemental wires, thedeformation ratios at the center part of the electric conductor were thesame in Sample 1 and Sample 2. However, the deformation ratios at theperipheral part were greatly different between Sample 1 and Sample 2. InSample 1, the deformation ratio at the peripheral part was smaller thanthe deformation ratio at the center part, which was kept as low as 18%of the value at the center part. To the contrary, in Sample 2, thedeformation ratio at the peripheral portion was the same as thedeformation ratio at the center part.

According to the above results, it was confirmed that, suppressing thecompression rate upon pressing of the raw wire strand makes it possibleto obtain an electric wire conductor having a flat cross-section havinga high vacancy ratio, with deformation ratios of the elemental wires atthe peripheral part smaller than at the center part.

[Flexibility of Covered Electric Wire]

Influence of a cross-sectional shape of the electric wire conductor toflexibility of the covered electric wire was examined.

(Test Method)

An electric wire conductor having a substantially circular cross-sectionand an electric wire conductor having a flat cross-section bothconsisting of an aluminum alloy were prepared in the same manner as inthe test “State of Cross-Section of Electric Wire Conductor” describedabove. Further, insulation covering were provided to prepare coveredelectric wires in the same manner as above. Cross-sectional areas of theelectric wire conductors were 35 mm² or 130 mm², respectively.

An aspect ratio of the flat cross-section was 1:3 for the conductor ofthe cross-sectional area of 35 mm², and 1:4 for the conductor of thecross-sectional area of 130 mm².

For each of the covered electric wires thus prepared, flexibility wasevaluated by measuring an opposing force.

Three-point bending was carried out for measuring the opposing force.That is, both ends of a covered electric wire having a length of 100 mmwere held firmly, and an opposing force incurred by bending a centerpart was measured with a load cell.

(Test Results)

Table 2 below shows measurement results of the opposing force obtainedfor each of the covered electric wires.

TABLE 2 Conductor cross- Cross- Opposing sectional area sectional shapeforce (N)  35 mm² Circular 32 Flat (1:3) 25 130 mm² Circlar 102 Flat(1:4) 88

According to Table 2, for each of the conductor cross-sectional areas,the opposing force was reduced when the sectional shape was changed fromcircular to flat. In other words, flexibility was enhanced. Even in thecase where the conductor cross-sectional area was as large as 130 mm²,flexibility was enhanced by flattening. In each of the conductorcross-sectional areas, the opposing force was reduced to 90% or lower byflattening; however, in the case of the large conductor cross-sectionalarea, the aspect ratio of the flat shape needs to be higher (width needsto be wider) to improve flexibility to the same degree.

[Heat Dissipation Performance of Covered Electric Wire]

A relationship between a heat dissipation performance of the coveredelectric wire and the shape of the electric wire conductor as well aspresence or absence of a heat dissipation sheet was examined by computersimulations.

(Test Method)

A computer simulation employing a thermal conductivity analysisaccording to a finite element method was used to estimate a degree oftemperature rise upon application of an electric current to a coveredelectric wire. Specifically, the covered electric wire was assumed as asample, in which an insulation cover made of PVC having a thickness of1.6 mm was formed on an outer periphery of three types of the electricwire conductors made of a copper alloy; one had a circularcross-section, one had a flat cross-section with an aspect ratio of 1:3,and one had a flat cross-section with an aspect ratio of 1:5. For theconductor having the circular cross-section, a conductor cross-sectionalarea was set to 134.5 mm², and for the conductor having the flatcross-sections, conductor cross-sectional areas were set to have threedifferent values based on 134.5 mm². Then, a current of 400 A wasapplied to each of the samples and a temperature rise for achieving asteady state was estimated by the simulation. A temperature of thesurrounding environment was set at 40 degrees C.

In addition, for the covered electric wire having a flat electric wireconductor with an aspect ratio of 1:5, a temperature rise was similarlyestimated also for a case where a heat dissipation sheet was disposed.As the heat dissipation sheet, two types of aluminum plates with athickness of 5 mm, having a width of 30 mm and 60 mm were employed. Aflat surface of the covered electric wire along the width direction xwas brought into close contact with a surface of one side of the heatdissipation sheet while aligning the center of the covered electric wirein the width direction x with the center of the heat dissipation sheetin the width direction.

(Test Results)

Values of temperature rise obtained by the simulation for each of thesamples are expressed in FIG. 9 as a function of a conductorcross-sectional area. FIG. 9 also shows approximate curves for thevalues.

According to FIG. 9 , the temperature rise of the electric wireconductor having a flat cross-section was kept lower than that of theelectric wire conductor having a substantially circular cross-section,that is, the heat dissipation performance was enhanced. In particular,as the aspect ratio of the flat shape was increased (the width wasincreased), the heat dissipation performance was enhanced. As a result,when an upper limit of the temperature rise was set at a predeterminedtemperature, the temperature rise may be suppressed below the upperlimit by forming the cross-section of the electric wire conductor intoflat and further by making the aspect ratio high, even if the conductorcross-sectional area of the electric wire conductor was made small. Forexample, when the upper limit of the temperature rise was set at 40degrees C., a lower limit of the conductor cross-sectional area was,approximately 135 mm² for the circular cross-section, approximately 125mm² for the flat cross-section with the aspect ratio of 1:3, andapproximately 120 mm² for the flat cross-section with the aspect ratioof 1:5.

Further, when the heat dissipation sheet was disposed on the coveredelectric wire having a flat cross-section, the heat dissipationperformance was further enhanced. In particular, the larger thecross-sectional area of the heat dissipation sheet was, the higher theheat dissipation performance improved. That is to say, when the upperlimit of the temperature rise was set at a predetermined temperature, aheat dissipation sheet having a large cross-sectional area couldsuppress the temperature rise below the upper limit, even if theconductor cross-sectional area of the electric wire conductor was madesmall. For example, when the upper limit of the temperature rise was setat 40 degrees C. and a width of the heat dissipation sheet was 30 mm, alower limit of the conductor cross-sectional area was approximately 95mm². In this case, the cross-sectional area of the heat dissipationsheet was approximately 1.6 times larger than the conductorcross-sectional area. On the other hand, when the width of the heatdissipation sheet was 60 mm, the lower limit of the conductorcross-sectional area was 67 mm². In this case, the cross-sectional areaof the heat dissipation sheet was approximately 4.5 times larger thanthe conductor cross-sectional area.

Although embodiments of the present invention have been described abovein detail, the present invention is not limited to the particularembodiment(s) disclosed herein, and various changes and modificationsmay be made without deviating from the scope of the present invention.

In addition, an embodiment has been described where the electric wireconductor has the vacancy ratio of equal to or more than a predeterminedvalue; however, an embodiment of the electric wire conductor does nothave the vacancy ratio described above may be presented, that is, anelectric wire conductor which contains a wire strand having a pluralityof elemental wires twisted together, and has a flat portion where across-section intersecting an axial direction of the wire strand isflat. Also in such an embodiment, forming the cross-sectional shape intoflat makes it possible to achieve both the improved flexibility and thespace-saving property compared with a case of the substantially circularcross-section. Further, also in such an embodiment, the above-mentionedfeatures relating to the electric wire conductor other than the vacancyratio can be suitably applied, for example, the cross-sectional shape ofeach elemental wire such as the deformation ratio, the material and theconductor cross-sectional area of the electric wire conductor, theaspect ratio of the electric wire conductor, and arrangement of both theflat portion and the low-flatness portion.

Furthermore, also the features relating to the covered electric wire andthe wiring harness as described above can be suitably applied.

LIST OF REFERENCE NUMERALS

-   1 Elemental wire-   10 Electric wire conductor-   10′ Raw wire strand-   20 Covered electric wire-   21 Insulator-   H Height-   W Width-   x Width direction-   y Height direction-   31 Heat Dissipation sheet-   32 Interposing sheet (Heat Dissipation sheet)-   33 Connection member-   41 Columnar member-   42 Tubular member-   51 Interior member-   52 Sound absorbing member

The invention claimed is:
 1. A wiring harness comprising: a firstcovered electric wire; and a second covered electric wire, wherein thefirst covered electric wire comprises a first electric wire conductormade of aluminum or an aluminum alloy and an insulator covering thefirst electric wire conductor, the first electric wire conductorcomprising a wire strand of a plurality of elemental wires twistedtogether, the first electric wire conductor having a flat portion wherea cross-section of the wire strand intersecting an axial direction ofthe wire strand has a flat shape; and wherein the second coveredelectric wire comprises a second electric wire conductor made of copperor a copper alloy and an insulator covering the second electric wireconductor, the second electric wire conductor having a lower flatnessand a smaller conductor cross-sectional area than the first electricwire conductor of the first covered electric wire.
 2. The wiring harnessaccording to claim 1, wherein: the flat portion of the first electricwire conductor has a vacancy ratio that is 17% or higher; and thevacancy ratio is defined as a ratio of vacancies not occupied by theelemental wires or any other substance in the cross-section of the flatportion.
 3. The wiring harness according to claim 1, wherein in thefirst electric wire conductor, deformation ratios of the elemental wiresat peripheral end parts in a width direction are 70% or lower ofdeformation ratios of the elemental wires at center parts.
 4. The wiringharness according to claim 3, wherein the deformation ratios of theelemental wires at the peripheral end parts are 50% or lower of thedeformation ratios of the elemental wires at the center parts.
 5. Thewiring harness according to claim 1, wherein the cross-section of theflat portion of the first electric wire conductor comprises a continuousvacancy capable of accommodating two or more of the elemental wires. 6.The wiring harness according to claim 1, wherein the cross-section ofthe flat portion of the first electric wire conductor comprises acontinuous vacancy capable of accommodating three or more of theelemental wires.
 7. The wiring harness according to claim 1, wherein:the cross-section of the flat portion of the first electric wireconductor includes opposing edges along a width direction of the flatshape being parallel to each other; and deformation ratios of theelemental wires in the first electric wire conductor are lower at endparts of the opposing edges of the flat portion than at a center part ofthe flat portion.
 8. The wiring harness according to claim 1, wherein:the first electric wire conductor comprises the flat portion and alow-flatness portion having a flatness lower than the flat portion; andthe flat portion and the low-flatness portion are continuously disposedin the axial direction.
 9. The wiring harness according to claim 1,wherein a number of the elemental wires contained in the wire strand ofthe first electric wire conductor is 50 or more.
 10. The wiring harnessaccording to claim 1, comprising a plurality of the first coveredelectric wires, wherein the plurality of the first covered electricwires are aligned along at least one of a width direction of an electricwire conductor and a height direction intersecting the width direction.11. The wiring harness according to claim 10, further comprising atleast one of a heat dissipation sheet disposed between the plurality ofthe first covered electric wires and a heat dissipation sheet commonlycontacting the plurality of the first covered electric wires.
 12. Thewiring harness according to claim 10, comprising a plurality of thefirst covered electric wires aligned at least along the heightdirection.
 13. The wiring harness according to claim 10, wherein:interposing sheets made of a heat dissipation material are disposedbetween the plurality of the first covered electric wires aligned alongthe height direction; and a connection member made of a heat dissipationmaterial is disposed mutually connecting the interposing sheets.
 14. Thewiring harness according to claim 1, wherein the conductorcross-sectional area of the second covered electric wire is 0.13 mm² orsmaller.
 15. The wiring harness according to claim 1, comprising aplurality of the first covered electric wires having different conductorcross-sectional areas, wherein the plurality of the first coveredelectric wires are aligned at least along a width direction of anelectric wire conductor, and have uniform length in a height directionintersecting the width direction.
 16. The wiring harness according toclaim 1, disposed along an outer periphery of a columnar member.
 17. Thewiring harness according to claim 1, housed in a hollow part of a hollowtubular member having an opening along a longitudinal direction.
 18. Thewiring harness according to claim 1, disposed under a floor of anautomobile to constitute a power-supply trunk line.
 19. The wiringharness according to claim 1, constituting a ceiling or a floor of anautomobile.
 20. The wiring harness according to claim 1, comprising aplurality of the first covered electric wires, wherein the plurality ofthe first covered electric wires are aligned at least along a widthdirection of an electric wire conductor, have uniform length in a heightdirection intersecting the width direction, and are disposed between aninterior member and a sound absorbing member of an automobile, disposingthe width direction along surfaces of the interior member and the soundabsorbing member.